Ebola outbreak: Here's what you need to know

International health authorities are trying to contain what is being called "the largest and most complex" outbreak of the deadly Ebola virus since its discovery.

Here is what you need to know about the disease.

What is Ebola?

Ebola — its proper name is Ebola virus disease — first appeared in two simultaneous outbreaks in 1976 in rural Sudan and rural Democratic Republic of Congo. The second location was near the Ebola River, hence the virus's namesake.

It's believed to be carried by certain species of fruit bats in Africa. They can spread Ebola to humans directly or indirectly through other animals.

How does Ebola spread?

People can acquire the virus from infected animals or humans.

Eating infected bushmeat or coming in close contact with bodily fluids of infected or deceased animals can transmit the virus.

But most cases in the current West Africa outbreak have come from human-to-human transmission, according to the World Health Organization. If a healthy individual's broken skin or mucous membranes come in contact with the bodily fluids of an infected individual or with an environment contaminated by an Ebola patient's bodily fluids, they can contract the virus.

"That means someone coughs in your face, you handle a body or you look after someone and don't have ideal infection-control methods. You get the virus on your hands, you touch your nose, your mouth," explains Dr. Jay Keystone, who works in the tropical diseases unit of Toronto General Hospital.

The virus can be spread through bodily fluids such as:

- blood

- stool

- urine

- saliva

- semen

Environmental hazards that could be infected with an Ebola patient's bodily fluids include:

- soiled clothing

- bed linen

- used needles

Once someone is infected, however, they can't spread the disease until the start showing symptoms, which generally appear between two to 21 days of transmission.

The disease is not airborne, meaning it cannot be transmitted simply by being in the same space as an infected individual.

What are the symptoms?

The virus attacks three types of cells: hepatocytes (functional cells of the liver), endothelial (which form the linings of the blood vesses) and phagocytes (absorb foreign particles).

Symptoms start to appear in stages. First, a person can experience sudden fever fatigue, muscle pain, headache and sore throat, according to WHO. Next, a patient will demonstrate vomiting, diarrhea, rash and symptoms of impaired kidney and liver function. Some people will have internal and external bleeding at this point as well.

How is Ebola treated?

There is no known treatment or licensed vaccine, but doctors can treat Ebola patients with some effectiveness and scientists have developed some experimental vaccines.

Doctors caring for Ebola patients can provide rehydration and treat specific symptoms, which improves the chances of survival.

Infected patients should also be isolated to prevent further spreading the disease.

Can someone with the virus be cured?

Not everyone who contracts the Ebola virus dies. The WHO pegs the fatality rate during this outbreak at around 50 per cent, while Dr. Keystone says it's a bit higher, at 60 per cent.

"It all depends on the quality of medical care," he explains. "The better the care, the more likely you are to survive."

Previous Ebola outbreak fatality rates have ranged between 25-90 per cent, according to WHO.

Where are there documented cases?

The current outbreak started in West Africa, with the first confirmed case in Guinea in December 2013, according to the European Centres for Disease Control and Prevention.

Guinea, Liberia and Sierra Leone have been most affected. By the end of September, Guinea had 950 confirmed cases and of those, 535 deaths; Liberia had 927 confirmed cases and 890 deaths; and Sierra Leone had 2,076 confirmed cases and 574 deaths, according to WHO.

Nigeria and Senegal had lower transmission rates, with only 19 confirmed cases and 7 deaths in Nigeria and a sole confirmed case in Senegal.

Nigeria's rapid response is to thank for its contained outbreak. Officials quickly isolated their first confirmed case and determined who the individual had come in contact with, the Centers for Disease Control and Prevention said.

At the end of September, a man in the United States was the first to be diagnosed with Ebola, the CDC confirmed. He had travelled from West Africa to Dallas, Tex.

What's different about this Ebola outbreak?

The WHO calls this Ebola outbreak "the largest and most complex" since the discovery of the virus.

It's unique because people in villages and major cities are being diagnosed, and almost all cases are from human-to-human transmission.

"First, there's a lot of cross-border travel. Whereas most other outbreaks have been isolated in the middle of virtually nowhere," says Dr. Keystone.

"Also, people in these countries don't trust the government. They don't believe in the infection. They hide their cases. If someone dies, they take [the body] home. And unfortunately the funeral procedures where you touch the body, and handle the body, markedly increases your risk. These cases are now more in central areas, cities rather than tiny villages. All of those reasons I think have compounded to make this a much greater outbreak."

How likely is it to appear in Canada?

With the United States diagnosing its first case of Ebola, it's natural to be concerned that the virus may come to Canada.

"I want to reassure everyone that the risk to Canadians remains very low," said Dr. Gregory Taylor, Canada's chief public health officer, at a meeting of federal, provincial and territorial health ministers this week.

Canada's Health Minister Rona Ambrose agreed, saying that "Canada is very well prepared" for dealing with infectious diseases.

Can I still travel?

The Canadian government recommends that citizens avoid non-essential travel to Nigeria, Guinea, Sierra Leone and Liberia.

But, the WHO says there's little risk for people travelling to West Africa on business or to visit family and friends.

"The most important thing is to try and stay away from people who are ill. You won't get Ebola unless the individual you're in contact with is sick," says Dr. Keystone.